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Discussion Starter #1
I'm considering buying this 96 Caravan @ 3.8L no rust and great body /interior.

current owner mention crank sensor/Cam sensor + speed sensor issue report via codes. Their Diagnostician suggest new Computer module. NEw PCM replaced ,sensors replaced, WITH THE EXCEPTION of the speed sensor. Battery was removed and codes are lost from memory. Van cranks and no start. Pump spins and hums and this van has been sitting since Feb 2012.

IF Speed sensor is faulty , can the van start/run?

Your thoughts?
 

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The input and output speed sensor are connected to the TCM, not the PCM. The TCM does put vehicle speed information out on the bus for the PCM, Cluster and other modules to use.
Is the PCM 5 volt line up with the key on? Does the 'ck eng' light come on and are there any fault codes?
If the vehicle has SKIM or VTSS, the new PCM would need the 4-digit secret key code entered to validate it. It would not be plug n'play.
Jumping into a new PCM too quickly is not good diagnostic practice, especially if it still doesn't start. It needs more diagnosis with a good scan tool to see what is going on.
 

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To add to the above:
Although the fuel pump appears to be spinning, I'd check the pressure anyhow. This vehicle should have a schrader valve on the fuel rail to check pressure, making that a very simple test.

I doubt that a 1996 vehicle would have SKIM and probably not VTSS, but that should be investigated.
 

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Correct about not having SKIM, I didn't look at the year closely enough.
If the VTSS option was embedded in the BCM then the new PCM should learn that it has VTSS after power up.
 

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Discussion Starter #5
Due to a number of cuts and splice in the original harness connecting sensors,coil pack & grounds to the computer... this 3.8L could never start. The previous owner was guided by questionable advice. Their vehicle was towed into the shop where the tech claimed the computer was fried so another reman was ordered. The replacement did not work and another was ordered. THe van still did not work. Crank + Cam PS were changed and still no spark. Owner exasperation led to buy a replacement vehicle. 8 Months later vehicle sits for sale, with little interest. I come across the ad and am intrigued with the description.
I roll up my sleeves and this is what I find: Ignition coil pack wire cut, Computer ground wire cut. Break in orange wire and no communication between Cam/Crank ps. Other Cam PS wire cut.

After removing the jumpers and tracing wires, the breaks are repaired, the sensors tested and computer harness secured. Battery reattached, van starts and dies. TPS is replaced and wiring checked. Van starts and idles rough.Codes are thrown and noted. Replaced MAP and missing relays + fuses, then restart. Success. No codes! Van runs and apparently was driven up to 80! She could not believe it would ever run again as this sat as a lifeless moneypit for nearly a year.

I am not a licenced tech .. but exercised care,dilgence and patience to solve this problem... But the hired guns failed the owners of this Van at considerable expense!

Note: The wiring harness the plugs into the PCM does NOT have retaining clips. So If I decide to buy this van, I will have to tie or biind the plugs to the computercome up with a large ZAP strap to retain a secure connection. Should I use liberal amount of dialectric grease on the pins/plug





Correct about not having SKIM, I didn't look at the year closely enough.
If the VTSS option was embedded in the BCM then the new PCM should learn that it has VTSS after power up.
 

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Great job of tracing the wiring and glad hear that you fixed it. Dielectric grease on the base of all pins is a good idea to keep moisture out and reduce the chance of corrosion.

It is amazing what due dilligence and a little patience can do. Nice work!
 

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Man, you deserve a hearty round of applause for your work. Like an old commercial on tv used to say "You are tenacious like bulldog." Keep up the good work.
 

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Discussion Starter #8
Great job of tracing the wiring and glad hear that you fixed it. Dielectric grease on the base of all pins is a good idea to keep moisture out and reduce the chance of corrosion.

It is amazing what due dilligence and a little patience can do. Nice work!
Follow up on this 3.8L that has been activated with new computer:

Went back today to test drive. IDles a bit unevenly. Slight hesitation upon acceleration. Vehicle has sat for 8 months. IT feels a bit choppy as if its running on 5. Got it up to 90 KM and van handles beautifully. There are no codes present. IF feels as if a valve is sticking or compression is off on one cyl but I couldn't verify. Any suggestions?

This new computer needs to relearn this van, but the idle seems as if there's something mechanical that's missing.


YOur thoughts...
 

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Probably a stupid question, but I'll ask it anyway. Did you drain all of the old gas out of the tank before you started driving it? If not, then that could be a lot of the problem. I'd suggest some techron fuel system treatment and some fresh gas just to start with.
 

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Discussion Starter #10
No the old fuel which has been in there for more than 8 months was just slightly below 1/4 on the guage. The code reader did not pick up any codes... but I'm wondering about Auto Idle Speed Control. The van does feel choppy under load which lead me to think that the AIS had nothing to do with it. I really need to spend more time with it. Compression testing would not be a bad idea which will clearly indicate head or ring issues.

I pulled the top of the resevoir bottle to see if there were any bubbles present and no steam out the tail pipe. Are the rear 3 spark plugs on the 3.8L just as much fun to remove as the 3.0L?

Probably a stupid question, but I'll ask it anyway. Did you drain all of the old gas out of the tank before you started driving it? If not, then that could be a lot of the problem. I'd suggest some techron fuel system treatment and some fresh gas just to start with.
 

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It sounds like a misfire from your description. A PCM may not detect and set a fault code for a misfire right after it is freshly connected, but may need to learn adaptive numerator first. It has to be driven in a particular way first.
Knowing which cylinder is affected may save you time and frustration.
http://www.motor.com...?article_ID=306
 

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Discussion Starter #12
Thank you Imperial Crown. I really appreciate that link and I think I may pursue this and buy the van : 96 Caravan ES 3.8L - 4speed 257,000 km ( 159,340 miles ) for $500.

The innova 3100 code reader indicated no codes,however not all routines had reported in which is why it flashed yellow instead of green. I could not see excessive moisture from tail pipe nor bubbles in reseviour tank as I feared head gasket. This would be the 1st Caravan with ABS and a factory security ( which I do not care for).

Fingers crossed!

It sounds like a misfire from your description. A PCM may not detect and set a fault code for a misfire right after it is freshly connected, but may need to learn adaptive numerator first.
Knowing which cylinder is affected may save you time and frustration.
http://www.motor.com...?article_ID=306
 

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Discussion Starter #13
My wife came joined me to see the van yesterday. The doors were locked with the exception of one driver's side sliding door left slightly ajar. Merely touching it set off the VTSS!!! Although this feature works,it is a real nuisance and can only complicate no start stiuations. The alarm disturbed the peace of the quiet neighbourhood for 3 min before becoming quiet and rearming itself.

The owner came out and unlocked the van and mentioned that the first time the van powered off was not far from home and had to be towed in. as previously mentioned, throwing parts , a reman. computer & repairing wiring eventually got the van to run.

I didn know that this van had VTSS until yesterday which might have been a contributing factor.
Is it also true that intermittent connection behind the instrument cluster on the 3.3/3.8L may also interfere with a start/run?

Knowing how much potential grief is cause by VTSS, can one disarm the VTSS by replacing both PCM and BCM with non security from a wrecker for 1996?

I'm beginning to wonder about this van before buying it how much potential grief I'm going to inherit despite the pristine body and luxurious features.

To add to the above:
Although the fuel pump appears to be spinning, I'd check the pressure anyhow. This vehicle should have a schrader valve on the fuel rail to check pressure, making that a very simple test.

I doubt that a 1996 vehicle would have SKIM and probably not VTSS, but that should be investigated.
 

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What you have is not really a VTSS issue but a failure of that particular door to lock. Even if you eliminate the VTSS, you'll still have the issue that the sliding door isn't locking. So fix the reason the sliding door isn't locking (probably bad contacts somewhere) rather than removing the VTSS which isn't an issue here. Unlike the other doors, the sliding doors don't lock when you press the remote or power door lock buttons until the slider is closed. If the sliding door isn't sensing that it is closed, it won't lock.

As for the cluster, even without the VTSS a dead cluster can interrupt the data bus and cause a no start.

I'd fix the issues that are there, not go looking for trouble trying to remove VTSS which would require computer replacements which may or may not re-learn the vehicle has VTSS because of the computer inputs.
 

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The VTSS is embedded into the PCM and BCM and can be eliminated by replacement with both modules from a non-VTSS vehicle, but I don't want to suggest that until you have proof that the VTSS has an issue.
Opening an unlocked door and setting of the alarm is a sign that the VTSS is on-duty and doing what it should. With the remote in your hand, you can cancel the alarm if it should occur accidentally or if there is a problem with a door switch, etc.
Until you really own it, you won't know the extent of electrical repairs that may be needed. Certainly reflow the cluster connector pin solder joints, clean the sliding door contacts and adjust the door ajar switches if you suspect a problem there or as a matter of 'maintenance'.
Make sure that all 4 doors and liftgate lock and unlock with the power locks. Make sure that both front and the rear 1/4 power windows work. Go through and try everything electrical in the vehicle making sure that everything works.
Head gaskets usually hold up well in these 3.3L/3.8L engines. Further misfire diagnosis is needed, if that is what's happening here.
The emission monitors (routines) are erased after a dead or disconnected battery and are only re-learned after driving 2 or 3 'good trips'. The adaptive numerator (I like that word) can be learned after a dead battery with a warm acceleration/deceleration drive cycle.
If you have a state inspection emission test requirement in your area, these will need to be learned and passed before you can pass a state inspection.
 

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Discussion Starter #16
It sounds like a misfire from your description. A PCM may not detect and set a fault code for a misfire right after it is freshly connected, but may need to learn adaptive numerator first. It has to be driven in a particular way first.
Knowing which cylinder is affected may save you time and frustration.
http://www.motor.com...?article_ID=306
Right you are!!!!!!!

Cold start this morning and drove off. I did notice that the van was vibrating or chugging when at rpm. This was noticed when A604 shifted into over drive or approx. 1500 rpm. Upshifting reduced the vibration. I was hoping to isolate the vibration to either misfire or transmission performance. I also noticed that the turn signals that were working yesterday were NOT today. Then after a while they did work.... so that's a mystery too. ( wiring ) Vehicle sat since FEB 2012 in Pacific Northwest Climate until briefly running no in October.

I picked up this van for a test drive and to take over to skilled veteran who could go over this 96 3.8L caravan ES with me. IT handled nicely and it felt that it was missing. I stopped and checked , still no codes reporting in. Then at his driveway, the van dies, barely starts and will not run. We push it into the bay. Further diagnosing pinpoints a couple of things:

COIL PACK:

Coil pack is warm after engine running for about 15 minutes. After stall Van still starts/stalls after 1 hour.
Intermittent spark on some cyllinders. All spark plug wires are NEW! About half of the terminals are energizing and the othes are dead!!!!!
Checking the wiring TO the coil pack indicates ALL wires have signal FROM PCM!
We conclude the coil pack is suspect.
Wiggling 4 wire harness at pack made no difference. ( did notice the insulation is broken there ... so that must be repaired ASAP)

vehicle was towed back to owners residence. I have indicated that I would be still be interested in the van is As is condition and asked what would be a reasonable figure.

so we'll see.


Good suggestion. Really appreciate your opinion!!!!!
 

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The next time that the turn signals don't work. Try playing with the ign switch. Move the key slightly toward 'start' and 'off'. The internal switch contacts may have oxidized from sitting and the contact wiper grease does thicken over the years. These can make for a poor or intermittent contact.
The hazard switch and turn signal switch contacts may have also oxidized from sitting. Working them on-off somewhat vigorously can 'scrub' the contacts clean for a good connection again.
An OBD II scan tool may show a 'pending' fault code or 1 trip failure before turning on the 'ck eng' light. The next failed trip should light the indicator. A misfire may also blink the 'ck eng' light as catalytic converter damage could occur.
Does the 'ck eng' come on during a bulb check when you first roll the ign key on?
The ign coil pack and the damaged wiring should be repaired. The coil pack may be the whole misfire problem.
 
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